Experimental Study On Mechanical Properties And Acoustic Emission Of Steel Fiber Broken Pebble Recycled Concrete

In response to our national call for sustainable development of resources strategy.To promote the scientific use of waste construction and waste pebbles from river cleaning in civil engineering.To reduce construction waste and large waste pebbles which had adverse impact on environment.This thesis made the broken pebbles recycled concrete by coarse aggregate which used as the pebbles and the waste concrete beams by crushed process in Handan area.Meanwhile,considering on shortcomings of the concrete and the coarse aggregate impacted on mechanical properties of broken pebble recycled concrete.This thesis add a little bit of steel fiber at the mixing broken pebble recycled concrete process.Using the steel fiber volume content(0%,1%,2%)and recycled coarse aggregate replacement rate(0%,10%,20%,30%,40%)as varable.Base on the acoustic emission nondestructive testing technology,under two different varable,this thesis reaserched the compressive and flexural properties of steel fiber broken pebble recycled concrete.The main researched contents and conclusions were as follows:(1)The coarse aggregate performance indexes were tested.Meanwhile,the each group test mix proportion was designed with the design parameters.(2)Under two different parameters,this thesis analyzed the compressive and flexural strength of steel fiber crushed pebble recycled concrete accossing the test.The results show that: The steel fiber broken pebble recycled concrete compressive and flexural strength will increase,with steel fiber volume content increasing.But,the compressive strength improved slightly,and in 1% and 2% steel fiber volume content,the strength improvement effect was similar.In addition,with the recycled coarse aggregate replacement rate increasing,the variation trend of steel fiber broken pebble recycled concrete compressive and flexural strength will go up then down.When the recycled coarse aggregate content was 30% and the steel fiber volume content was 1%,2% respectively,its compressive and flexural reached maximum value respectively.(3)Based on the measured flexural load-deflection curve of steel fiber broken pebble recycled concrete,under two different parametrics,this thesis analyzed the influence on variation trend of load-deflection curve and bending toughness.The results show that: When recycled coarse aggregate replacement rate was less than 30%,the steel fiber broken pebble recycled concrete measured load-deflection curve became fuller,and the bending toughness increased significantly,with the content of steel fiber and recycled coarse aggregate increasing.Nevertheless,both of the load-deflection curve plumpness and the bending toughness will decrease,when the recycled coarse aggregate replacement rate was above 30%.(4)On the compression and bending failure process of steel fiber broken pebble recycled concrete,This thesis used AE nondestructive testing technology,to carry out the AE damage monitoring test on these process.The results show that: The compression and bending process of steel fiber broken pebble recycled concrete can compose with elastic stage,crack propagation stage,failure stage.In these three stages,the activity of AE signal increases successively.Compared with the compression test piece group without steel fiber,the distribution of damage positioning points of compression test piece group with steel fibe was relatively scattered.At the same time,compared with the compression and bending specimens without steel fibers,the compression and bending specimens with steel fibers had more damage anchor point,and the activity of parameter signal(energy,ringing,amplitude,impact)was more higher.In addition,from the point of AE parameter analysis results,with the steel fiber content and recycled coarse aggregate content increasing,the initial damage of steel fiber broken pebble recycled concrete will increase.But a moderate amount of recycled coarse aggregate replacement rate could effectively improve its binding strength,From the test results,the best replacement rate was 30%.(5)This thesis respectively analyzed the cumulative energy and ringing of compression and bending of steel fiber broken pebble recycled concrete.The results show that: The cumulative energy and ringing of steel fiber broken pebble recycled concrete in compression process,and the cumulative energy and ringing in bending process,which variation rule were positively correlated with its compressive strength and flexural strength variation rule respectively.In addition,under the two different parametric,the compression damage evolution model of steel fiber broken pebble recycled concrete was established by this thesis with the accumulated energy of acoustic emission.After inspection,the fitting value and the actual measured value had small difference,which can provide reference for its subsequent related research and application.